Project Summary/Abstract The general purpose of this proposal is to provide training opportunities to learn how epidemiological methods can be applied to the investigation of health disparities among children in low-income settings. Specifically, the proposed study investigates how iron deficiency relates to child development in infants and toddlers in rural India. This training grant provides the opportunity to gain the knowledge and skills necessary to become an independent researcher by integrating coursework in child health, nutrition, and epidemiologic methods with mentorship in the application of skills to a problem of global significance in the context of professional development. Iron deficiency is the most common micronutrient deficiency worldwide; it occurs disproportionately among children under five years of age. Nutrition adequacy (including iron-rich food) is essential for adequate brain development. Early child (brain) development has short- and long-term effects on health and productivity. Based on the social-ecological model, factors previously identified to impact child development include stunting (child level), maternal education (interpersonal) and home environment (family/household). Although cohort studies have provided compelling evidence supporting an association between iron deficiency and child development, intervention trials have found inconsistent evidence, frequently attributed to methodological limitations. There is therefore a need for further investigations and for understanding mechanisms of the association between iron deficiency and child development. The proposed study seeks to assess the relations between iron deficiency and child development in infants and toddlers. The study aims to examine: 1) whether there is an association between iron deficiency and children's cognitive, motor, and socio-emotional development at enrollment and over 12-month follow-up, 2) whether the relation between iron deficiency and children's development varies by children's stunting, maternal education, and the home environment, and 3) whether the duration of iron deficiency impacts children's development. Regression modeling will be used to assess baseline associations, and linear mixed effects models will be used for longitudinal analyses. The proposed study is unique in the use of standardized and highly controlled methods of iron status (venous blood draw and analysis), child development (standardized tests administered by trained psychologists) to assess the relation between iron deficiency and child development, and collaboration with investigators in a low-income country. This project is in line with NICHD's priority to ?is to advance fundamental and clinical knowledge about maternal health and problems of child development?.